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Organ system histology
Arteriole, venule and capillary histology
Artery and vein histology
Cardiac muscle histology
Adrenal gland histology
Pituitary gland histology
Thyroid and parathyroid gland histology
Eye and ear histology
Nasal cavity and larynx histology
Small intestine histology
Lymph node histology
Skeletal muscle histology
Central nervous system histology
Peripheral nervous system histology
Ureter, bladder and urethra histology
Cervix and vagina histology
Fallopian tube and uterus histology
Mammary gland histology
Prostate gland histology
Testis, ductus deferens, and seminal vesicle histology
Bronchioles and alveoli histology
Trachea and bronchi histology
Bones are composed primarily of an extracellular calcified material called the bone matrix or collagen matrix.
It also has three main types of cells: osteocytes, osteoblasts, and osteoclasts.
Osteocytes are found in cavities or lacunae between the layers of the bone matrix and assist with the nutrition of the bone.
Osteoblasts are found mostly along the surface of bones, but also within the bone matrix itself.
They’re responsible for both synthesizing and mediating the mineralization of the bone matrix.
Osteoclasts are large multinucleated cells that are responsible for removing calcified bone matrix and allow for the constant turnover and remodelling of bones.
Morphologically, there are two main types of bone.
The compact or cortical bone is the dense portion that’s found closer to the surface of bones.
The deeper portion of bones have interconnecting cavities and is called the cancellous or trabecular bone.
In this electron microscopy or EM image of the tibia, the compact bone is also blue, and the more central trabecular bone is yellow. Microscopically, both compact and trabecular bones will be organized or arranged in two forms.
Layered or lamellar bone has a bone matrix that’s arranged in sheets.
80% of lamellar bone is found within the compact bone and only 20% is found within the trabecular bone. The more immature woven bone, has collagen fibers that are arranged randomly.
This form of bone is found mostly within developing and growing bones, as well as bones that have healed after being fractured.
Alright, let’s compare sections of a long bone and a flat bone.
This long bone is a partial cross-section of the head of a long bone, and the flat bone is a cross-section from the skull.
Bone is a connective tissue that consists of an organic matrix (containing collagen and proteoglycans) and inorganic minerals (primarily hydroxyapatite). The organic matrix provides the tensile strength, and the inorganic minerals provide the compressive strength.
Bone also contains three major types of cells, which are osteocytes, osteoblasts, and osteoclasts. Bone undergoes continuous remodeling throughout life. Osteoblasts produce a new bone matrix, which is mineralized by osteocytes. Osteoclasts resorb old bone matrix. This process of remodeling ensures that bones are constantly adapting to changes in mechanical loading.
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